352 VEGETABLE PHYSIOLOGY 



CHAPTER XXII 



THE PROPERTIES OF VEGETABLE PROTOPLASM 



The influence of the environment upon the structure of 

 plants we have seen to be far-reaching. Different con- 

 ditions of the surroundings are followed by differences of 

 structure, which are greater in proportion as the time 

 during which those conditions act is more and more pro- 

 longed. The living substance of the plant is clearly the part 

 influenced by the environment, for we have seen that the 

 skeleton and other non-living parts of the plant owe 

 their construction to its activity. We may therefore with 

 advantage pause at this point to examine a little more 

 closely the properties which are exhibited by vegetable 

 protoplasm. 



We have seen throughout all the foregoing chapters 

 that all the processes which conduce to the well-being of 

 the plant are, to a large extent, if not entirely, under the 

 control of the living substance. Though the absorption 

 of the raw materials of its food from the air and the soil is 

 due to physical processes, these are nevertheless largely 

 regulated by the behaviour of the protoplasm under all sorts 

 of varying conditions. The manufacture of food from these 

 crude materials, and its subsequent distribution, the accumu- 

 lation and dissipation of energy, the processes of nutrition 

 and growth, are all subject to the same regulation. 



But there are also other properties of protoplasm which 

 have not so far been more than incidentally referred to. 

 The plant exhibits particularly the power of appreciating 



